Low-temperature distillation of coal



Oct. 6, 1953 J. A. PHINNEY 2,654,698

LAW-TEMPERATURE DISTILLATION OF COAL Filed May a, 1950 PRODUCT CHAR CRUSHER I ELUTRIATOR ROTATING KILN v INVENTOR JOHN A. PHINNEY FLUE GAS

Patented Oct. 6, 1953 LOW-TEMPERAT John A. Phinney,

;to Pittsburgh Pittsburgh, Pa.,

URE DISTILLATION OF COAL Mount Lebanon, Pa,., Consolidation Coal Company, a corporation of Pennsylvania assignor Application May 3, 1950, Serial No. 159,727

1 This invention relates to the distillation of coal and, more particularly, to the low temperature distillation of coal to yield tar, a high B. t. u. gas, and solid product or char composed of particles having a substantially uniform volatile matter content.

it has previously been proposed to distill coal at low temperatures by contacting the coal in finely divided form with sufficient hot solid distillation residue from previously distilled coal to heat the fresh coal to its distillation temperature. In such distillation systems, the solid product is a mixture comprising carbonaceous distillation residue which has been subjected only to the average temperature of the distillation zone and carbonaceous distillation residue which has been heated to a temperature substantially higher than the average temperature in the distillation zone. the total solid product is a mixture of two carbonaceous distillation residues having different volatile matter content, Since the product char represents a major proportion of the total distillation yield, it is imperative that this product possess properties rendering it suitable for use in one or more industrial applications. Generally, the most important industrial application is that of fuel for power plants. In such plants, it is highly desirable that the fuel have a uniform volatile matter content which is as high as possible, preferablyin theneighborhood of 10% or higher. Unfortunately, the volatile matter content of the solid product mixture obtained by previous systems of; this type is nonuniform and generally is less than, 10%. 7 Accordingly, theprimary object. of this invention is to provide a process of distillingcoal. at low temperatures which will yield in additionto tar and high B; t. u. gas a. solid char product,

composed of particles having substantially the same volatile matter content which at least, 10%;

In accordance with the present invention, fine-T lydivided fresh coal and preheated finely divided carbonaceous distillation residue from previously distilled coal are fed to a distillation zone. The temperature of the preheated; distillation residue is 'sufficiently highto raise the temperature of the fresh coal to the point where it distills... The size consistencies ofthe fresh coal. and of the preheated distillation residue are sufficiently difierent to permit the ready separationof the preheated; distillation residue fromthe distillation-residue produced from the fresh coal inth j distillation zone.

The twostreams of differentlysized -solids are thoroughlymixed in--the distilla 7 Claims. (Cl. 2029) tion zone to permit the transfer of heat from the preheated residue to the fresh coal whereby distillation of the latter is effected. The volatile products including tar and gas are separately recovered from the mixture of solid products. The latter mixture, consisting of particles of two different size consistencies, is conducted to a s'ep aration zone and there separated by any suitable means, such as elutriation into its two differently sized components. The freshly produced distillation residue is then discharged as product While the preheated residue is recycled to a combustion zone where at least a portion of the carbon content is oxidized to elevate the temperature of the residue to the desired level. to the distillationzone to repeat the operation.

Since the carbon content of the recycled residue-is continuously being depleted in the combustion zone, it is necessary from time to time to discharge a portion thereof in the form of ashor low volatile residue, and replenish the residue from previously distilled coal of substantially the same size consistency. The latter may be ac compl-ished by crushing a portion of the freshly produceddistillation residue to the desired size and feeding it to' the system or by circulating a predetermined amount of finely divided fresh coal of the same size consistency as the recycled residue. The distillation of this latter coal will provide the necessary residue to replace that discharged. Or, if more convenient, the recycled distillation residue may be replenished from an outside source of previously distilled coal.

In the preferred embodiment of my invention the recycled distillation residue has a size consist'ency sufliciently smaller than that of thefresh coal fed tothe distillation zone to permit its ready'separation from the solid=distillation of the fresh coalby 'el'utri'ationl In such an embodimerit; the gas used to elutriate the difierently sized particles may serve to carry the finer sized recycled residue to the combustion zone. Furthermore, flue-gas from the combustion zone can be employed'a's the elutriation gas, thus providingaself-sufficient system.

' The practice ofmyinvent'ionas briefly outlined" 'a-b'ove preservesi all the advantage of distilling" coal by-direct contact with hot distillation-residue and 'at the same time yields a char product" composed; ofparticles, all of which havesubstan This content is many the same volatile content. alsosubstantially higher than that otherwise p'o's*- sible. Forexample, instead of'a volatile matter content of 8 for the charjproduced without sep arati'c'nof thedifferent distillation residues, a'v'ol" It is then recycled through conduit 32.

atile matter content of 15% or more may be obtained by the practice of this invention under otherwise similar conditions. Such an improvement increases considerably the value of the char as a fuel for power plants and the like.

For a better understanding of my invention, reference is had to the following detailed description and drawing in which-is shown diagrammatically a preferred embodiment of my invention.

The apparatus which I prefer to employ for the practice of my invention and its operation will now be described. Numeral I designates a horizontal cylindrical retort mounted for rotation about its longitudinal axis. This retort and its mode of operation is more fully described in the copending application of C. E. Lesher, Serial Number 11,964, filed February 28, 1948. Finely divided fresh coal of a predetermined size consistency is fed into a retort from a storage hopper i2 through a conduit I4. Concurrently therewith, preheated distillation residue from previously distilled coal is fed into the same retort through a conduit IS. The size consistency of this preheated residue is sufiiciently smaller than that of the fresh coal to permit its ready separation by elutriation from the distillation residue of the fresh coal, as will be more fully described later. The retort is rotated to effect mixing of the two types of solids to permit transfer of heat from one to the other. The temperature of the preheated residue is sufficiently high to insure that the average temperature reached in the retort is the distillation temperature of the coal. In general, the temperature of the distillation zone lies in the range of 850 to 1050'F.

The volatile products, including gas, tar and the mixture of solid products, are discharged from the retort into a separation zone I8. Here. the volatile products are led through a cyclone separator 2a to a discharge conduit 22. The gas and tar may subsequently be separated in conventional fashion. The solids in the separation zone 18 and also those recovered in the cyclone separator 28 are conducted through conduits 24 and 25, respectively, to an elutriator 28. Elutrirv tion gas is introduced in the elutriator at the bottom thereof through a conduit 30. The v locity of this gas is so regulated as to effect separation of the two differently sized particles forming the mixture of solids content therein in a manner well'known in the art. The larger sized particles consisting substantially entirely of fresh distillation residue from the coal feed of theretort is discharged from the bottom of the elutriator as high volatile matter product char The liner sized particles consisting ofthe preheated residue and any fresh distillation residue that may have been reduced to the size of the preheated residue is conveyed by the elutriation V gasthrough a conduit 34 to a combustor 36. This combustor comprises a vertical elongated yessel comprising a lower section 38 of substantially cylindrical conformation and a higher section "it likewise of substantially cylindrical conformation but of greater diameter than the lower section. The solids are introduced into the lower section38 where they form a bed t rou which air or other oxidizing gas is circulated from a feed conduitdZ. The velocity of the air i regulated to effect fluidization of the solids in the combustor. The solids are oxidized sufficiently to raise the temperature of the mass of solids coal which exhibit'a tendency to agglomerate in to that desired. This temperature is substantially higher than the average temperature prevailing in the distillation retort Ill. Its exact value will depend upon the temperature desired in the distillation zone and upon the quantity of residue recycled. The products of combustion or flue gas are removed from the combustor through a cyclone separator 44 to a discharge conduit 36. Solids removed from this gas in the cyclone separator are returned to the bed through dip-leg 48. The hot distillation residue is discharged into conduit 16 for readmission to the distillation retort to repeat the above cycle.

A portion of the flue gas from discharge conduit 46 may be employed as the elutriation gas for the elutriator 28. In this case, the conduit 30 is connected to conduit 45 with a suitable valve arrangement (not shown) being provided to regulate the quantity of gas required. A pump 50 is disposed in the line 3!! to develop the necessary pressure and circulation rate. The conduit 3!] may likewise be arranged in heat exchange relation with the inlet air conduit 42 to make use of the heat content of the flue gas for preheating the air.

The recycling of the finer sized distillation residue through the combustion zone results in a depletion of the carbon content of the solids. This depletion may be carried to the point where substantially all of the carbon on the residue is oxidized to produce the necessary heat of distillation, but not necessarily. A certain amount of this depleted residue is discharged from the system through conduit 52. Replenishment of this discharge material may be accomplished in a number of different "ways. Preferably, a predetermined amount of fresh coal fines having size consistency corresponding to that of the recycled residue is introduced into conduit I i, which carries the main portion of the coal, from a storage hopper 54 through conduit 56. These coal fines are distilled in retort l0 and discharged therefrom as distillation residue having. a size substantially the same as that of the preheated residue fed to the retort. These fines are added to the recycled material by the elutriation of the solid products in the elutriator 28. Another procedure is to crush a portion of the high volatile product char removed from the discharge conduit 32 through a conduit 58 to a crusher 69. This crusher effects reduction of the particle size sufficiently to convert it to the size consistency of the recycled residues. Following crushing, the fine res due. is returned to the elutriator 28 through conduit 62.

In order for the above described system to operate effectively, it is necessary that the coal be distilled in the retort [0 under non-agglomerating conditions. While this presents no problem in the .case of many, coals, there are classes of the neighborhood of their'distillation temperature. This agglomeration may be prevented in the manner fully described in the above mentioned copending application. The amount of recycled char is regulated so as to provide sufficient diluent to prevent the coal from agglomerating when passing through the plastic range. In the case of highly caking coals, the inert residue and fresh coal are fed separately into the rotating kiln and onto the top of a bed of char maintained at a predetermined level in the retort. In such a system the fresh coal is flash distilled so rapidly through its plastic range that no opportunity is presented for agglomeration 'size"coiisisteticy of 17x" with about i i-0% "'tIianBO'mesh. The preheated residiiehas 'ajsi'ze' consistencyof 3b mesh xo;

Table f 1 For case A. this is amixtureofhigh volatile-andlow volatile' ohar While for c'a's'eB it ise'xclusivly"and uniformly high volatile chaff It Will be noted that v the yields I of char in {the two" cases are substantially the] ame y etthe volatile matter content or the high- Volatile giliaZ-r in "case B :i's 14.7% contrasted: with a vqlatile iii'atterfo'f 8.1%- for the mixed 'solid iirodiict-vch'ar i'r'i ca's'eA.

According tb the provisions of the paten t statates, I have explained the principle, z p 're'fer'red gonstruo tioh, and mode of bperati'on of my i nve'nti'on' and have illustrated and deseribed what I now consider to represent its bes't einbodi However; I desireto have it 'unders'too'd that; within the sb'ofpe o'f-theapiiendedblaims, the in vention maybe practioed otheijwise thanasspedifically illus tiet ted 5nd desefibd.

I claim: I a k .1; In the' process for low te'mpratiire distillation of coal to yield gaseous and liquid pr gducts and'a solid distillation .residiiefcbhipbsed of particles having siib's'tahtially"the,' saline Volatile matter content; the steps c'dinplis'iiig' rdfilfatin'g fihel y"divid'ed'freshi'cdal or a'jpreaete ned' tarticle size consist'e'rieythroii'gh' a isti a 1011 fzone'; iiii'biil'atihg' preheated finely divided pfy'ioiisly distilled coal thzoughQsaiddistillation zone in sh balfh'ing derived "splely item-,5 a pretiotsiy di tin'ed' teal, said --..pre-

amount of'distillat'ion residue including; previous- 11y" distilled etal present in said distillation =zone atifaiiy' dife time lpeirig;- siiflicient; to: prevent- :agglomeration of said fresh eoal zbydilutiomthereef, reboxieringithe gaseous and liquid produets of dis= tillationgseparating the distillationresidueof said fresh coal -from--saidsolid products, circulating. at leasta portion-of=-.-the remaining-s0lid products to a combustiemhonewhere the ftem ,perature is raisedby; partial oxidatiomrrecycl ing atleastaportmn '0? the partiallyo'xidiz'ed S01id$ to .thedistillatiomzoneato serve as said preheated previously distilled-coal; and :repl-enishingrsaid reeycled- -previously distilled coal with ia pofti'oii of'the 'disti'llation residue;

2.- In the :p1t0cess *fiar- :low 'temizieratiire rdistil lation of coal-"to yield *gase'ous :and- "liquid prod ucts =anda.-se1id :dis-tillaition residue composed of particles I "having *substantia'l-ly i'thesaine I volatile matter content, the steps'compris-ing fcirciilating finely: dividedfresh cealeof a predetermined size consistencythrough adistillation zor'ie'g air-'- culaiting preheated finel-y divide'd prieviousiy distilled coal "through said" distillation zonem 1direct heat-exchange relation with saidfre'sh eoal so as toform acmixture "of solid 'siproduets-" with said-fresh coal; the heatrequired effect dis tillaztionedf said fresh coal 'being derived solely from said previously distilled -icoal, said p're: viouslydistilled coail' having a," particle size consistency suflieiently :diifereri-tfrom that of said .f-resh 'coal to permit itsi'ready separation from the distillation-'zresidiie '.of said fresh c'oal; -cireulating anothe'r but'sma'ller-amouritaof fresh coal-of substantially the same rs-i'ze .Econsisteneyl "as said previously distilled 1 coal sin xdirec't' heat exchange relation therewith;the-ztotalamount *of distillatiefnresidueincluding-.previeusly distilled c'oal present insaid distillation :zo'n'e air-any "one time being-sumcient to prevent-sagglehiei ation 0f said fresh "coal by idilutionfthereofg recmrer-irig the gaseous and liquid products of distillation-, separating the distillation r'esidiie o'f said first mentioned coal from said i'solid products; circulating the 'restof the so'lideprodiicts to :a combustion zone-where their temperature' is raised byi'ipartialoxidation, andwreturninga at least 7 a" portion of the *p'artially okid'izedarsolidsto said distillationczone t0"SB1V--L8S said preh'eatedpi'eviou'sly distilled "coal;

:3; 'I heproces's'ior low-temperature distillation :df coal in a .harizbntal etilin drieal retort mounted for "rotation atte-t ns: ldngitiidhial ases whieh com sf eed ihg' i'ritb o 4 end of said rthrt fiiiel d ed fi es'lil coa'l d preheated firi'ely divided' prevfipiislir' distilled war which is at siifii'die'ritly' hi'gh telnpfatiireto raise theiteinp'erature of 'the fresh coal to a distillation Itempeiatiire, the particle consistency of "said pfevioiisly distilled 106231 a shliioie'ntli smaller 7 r tion accomplished, the total amount of distillation residue including'previously distilled coal present in said distillation zone at any one time being sufi'icient to prevent agglomeration of said fresh coal by dilution thereof, separately recovering the volatile and solid products, conducting said solid products to an elutriation zone, circulating gas through said elutriation zone under elutriating conditions, Withdrawing the larger sized particles of freshly distilled coal from'said elutriation zone, circulating the finer sized solid particles to a combustion zone, passing an oxidizing gas through said finer sized particles under fluidizing conditions, recycling at least a portion of said partially oxidized particles to said retort to serve as said preheated previously distilled coal, and replenishing said recycled solid particlesby previously distilled coal of the abovementioned size consistency.

4. In the process for low' temperature distillation of coal to yield gaseous-and liquid products and a solid distillation residue, the steps comprising mixing in a distillation zone fresh finely divided coal with finely divided preheated distillation residue from said coal in such proportions that the average temperature of the re sulting mixture is at a distillation temperature of the fresh coal, the heat required to effect distillation of said fresh coal being derived from said preheated distillation residue, and the average particle size of said preheated residue being sufficiently smaller than that of said fresh coal to permit separation by elutriation, distilling the coal, the total amount'of distillation residue including previously distilled coal present in said distillation zone at any one time being suificient to prevent agglomeration of said fresh coal by dilution thereof, separately recovering the volatile and solid products, separating from said solid products that portion having a particle size within the range of the preheated residue fed to the distillation zone, circulating said portion to a combustion zone, partially burning said portion to raise its temperature above the average temperature in said distillation zone, and recycling this heated portion to said distillation zone to serve as said preheated residue.

5. In the process for low temperature distillation of coal to yield gaseous and liquid products and a solid distillation residue composed of particles having substantially the same volatile matter content, the steps comprising circulating finely divided fresh coal of a predetermined particle size consistency through a distillation zone, circulating preheated finely divided pre viously distilled coal through said distillation zone in a direct heat exchange relation With-said fresh coal so as to'forma mixture of solid products with said fresh coal, the heat required to effect distillation of said fresh coal being derived solely from said previously distilled coal, said previously distilled coal having a particle size consistency smaller than that of said fresh coal to permit its ready separation by elutriation from the distillation residue of said fresh coal, circulating another but smaller amount of fresh coal of substantially the same size consistency as said previously distilled coal through said distillation zone in direct heat exchange relation therewith, the total amount of distillation residue including previously distilled coal present in said distillation zone at any one time being suificient to prevent agglomeration of said fresh coal by dilution thereof, recovering the gaseous and liquid products of distillation, conducting the:

solid products to an elutriation zone, circulating gas through said solids in said elutriation zone under elutriating conditions, withdrawing the larger particles of distillation residue of said fresh coal from said elutriation zone, circulating the finer sized particles to a combustion zone, passing an oxidizing gas through a bed of said finer sized particles under fluidizing conditions, and returning at least a portion of these oxidized particles to said distillation zone to serve as said preheated previously distilled coal.

6. In the process for the low temperature distillation of coal to yield gaseous and liquid products and a solid distillation residue composed of particles having substantially the same volatile matter content, the steps comprising circulating finely divided fresh coal of a predetermined particle size consistency through a distillation zone, circulating preheated finely divided previously distilled coal through said distillation zone in direct heat exchange relation with said fresh coal so as to form a mixture of solid products with said fresh coal, the heat required to effect distillation of said fresh coal being derived solely from said previously distilled coal, said previously distilled coal having particle size sufficiently smaller than that of said fresh coal to permit its ready separation by elutriation from the distillation residue of said fresh coal, the total amount of distillation residue including previously distilled coal present in said distillation zone at any one time being sufficient to prevent agglomeration of said fresh coal by dilution thereof, recovering the gaseous and liquid products of distillation, conducting the solid products to an elutriation zone, circulating gas through said solids in said elutriation zone under elutriating conditions, withdrawing the larger particles of distillation residue of said fresh coal from said elutriation zone, circulating the finer sized solid particles to a combustion zone, passing an oxidizing gas through a bed of said finer sized particles under fluidizing conditions, recycling at least a portion of these oxidized particles to said distillation zone to serve as said preheated previously distilled coal, and replenishing said recycled previously distilled coal with a portion of the distillation residue.-

7. In the process for low temperature distillation'of coal to yield gaseous and liquid products and a solid distillation residue composed of particles having substantially the same volatile matter content, the steps comprising circulating finely divided fresh coal of a predetermined particle size consistency through a distillation zone, circulating preheated finely divided previously distilled coal through said distillation zonein direct heat exchange relation with said fresh coal so as to form a mixture of solid products with said fresh coal, the heat required to eifect distillation of said fresh coal being derived solely from said previously distilled coaLsai-d previously distilled coal having a particle size consistency sufficiently smaller than that of said fresh coal to permit its ready separation by elutriation from the distillation residue of said fresh coal, the

total amount of distillation residue including previously distilled coal present in said distillation zone at any one time being sun eient to prevent agglomeration of said fresh coal by dilution thereof, recovering the gaseous and liquid products of distillation, conducting the solid products to an elutriation zone,'circulating gas through said solids in said elutriation zoneunder 'elutriatin'g' conditions, withdrawing the particles of distillaton residue of said fresh coal from said elutriation zone, crushing a portion thereof to a size consistency corresponding to that of said previously distilled coal and returning it to said elutriation zone, circulating the finer sized particles from the elutriation zone to a combustion zone, passing an oxidizing gas through a bed of said finer sized particles under fiuidizing conditions, and returning at least a portion of these oxidized particles to said distillation zone to serve 10 as said preheated previously distilled coal.

JOHN A. PHINNEY.

References Cited in the file of this patent UNITED STATES PATENTS 15 Number Name Date 1,664,723 Young Apr. 3, 1928 1,698,345 Puening Jan. 8, 1929 1,899,887 Thiele Feb. 28, 1933 20 1,905,055 Puening Apr. 25. 1933 Number Number Name Date Hemminger Nov. 7, 1944 Johnson Jan. 29, 1946 Johnson Jan. 29, 1946 Johanson May 13, 1947 Berg May 11, 1948 Keith July 20, 1948 Davies et a1. Feb. 22, 1949 Sweetser et a1. Apr. 26, 1949 Peck Aug. 30, 1949 Welty Jr Jan. 16, 1951 Roetheli Dec. 18, 1951 Creelman Aug. 5, 1952 Matheson Oct. 14, 1952 Lesher Dec. 16, 1952 FOREIGN PATENTS Country Date Great Britain Aug. 5, 1926 

1. IN THE PROCESS FOR LOW TEMPERATURE DISTILLATION OF COAL TO YIELD GASEOUS AND LIQUID PRODUCTS AND A SOLID DISTILLATION RESIDUE COMPOSED OF PARTICLES HAVING SUBSTANTIALLY THE SAME VOLATILE MATTER CONTENT, THE STEPS COMPRISING CIRCULATING FINELY DIVIDED FRESH COAL OF A PREDETERMINED PARTICLE SIZE CONSISTENCY THROUGH A DISTILLATION ZONE, CIRCULATING PREHEATED FINELY DIVIDED PREVIOUSLY DISTILLED COAL THROUGH SIAD DISTILLATION ZONE IN DIRECT HEAT EXCHANGE RELATION WITH SAID FRESH COAL SO AS TO FORM A MIXTURE OF SOLID PRODUCTS WITH SAID FRESH COAL, THE HEAT REQUIRED TO EFFECT DISTILLATION OF SAID FRESH COAL BEING DERIVED SOLELY FROM SAID PREVIOUSLY DISTILLED COAL, SAID PREVIOUSLY DISTILLED COAL HAVING A PARTICLE SIZE CONSISTENCY SUFFICIENTLY DIFFERENT FROM THAT OF SAID FRESH COAL TO PERMIT ITS READY SEPARATION FROM THE DISTILLATION RESIDUE OF SAID FRESH COAL, THE TOTAL AMOUNT OF DISTILLATION RESIDUE INCLUDING PREVIOUSLY DISTILLED COAL PRESENT IN SAID DISTILLATION ZONE AT ANY ONE TIME BEING SUFFICIENT TO PREVENT AGGLOMERATION OF SAID FRESH COAL BY DILUTION THEREOF, RECOVERING THE GASEOUS AND LIQUID PROUDCTS OF DISTILLATION, SEPARATING THE DISTILLATION RESIDUE OF SAID FRESH COAL FROM SAID SOLID PRODUCTS, CIRCULATING AT LEAST A PORTION OF THE REMAINING SOLID PRODUCTS TO A COMBUSTION ZONE WHERE THE TEMPERATURE IS RAISED BY PARTIAL OXIDATION, RECYCLING AT LEAST A PORTION OF THE PARTIALLY OXIDIZED SOLIDS TO THE DISTILLATION ZONE TO SERVE AS SAID PREHEATED PREVIOUSLY DISTILLED COAL AND REPLENISHING SAID RECYCLED PREVIOUSLY DISTILLED COAL WITH A PORTION OF THE DISTILLATION RESIDUE. 